1. Field of the Invention
The present invention relates generally to bar code symbol reading systems and, more specifically, to systems having one or more base stations and one or more hand-held bar code symbol readers equipped to communicate with these base stations.
2. Brief Description of the Prior Art
Bar code symbols have become widely used in many commercial environments including point-of-sale (POS) stations in retail stores and supermarkets, inventory and document tracking, and diverse data control applications. To meet the growing demands of this technological innovation, bar code symbol readers of various types have been developed for scanning and decoding bar code symbol patterns, and for producing symbol character data to be used as input in automated data processing systems.
In general, prior art hand-held bar code symbol readers using laser scanning mechanisms can be classified into two major categories. The first category includes manually-actuated trigger-operated systems having lightweight laser scanners which can be held in a user""s hand. The user positions the hand-held laser scanner at a specified distance from an object bearing a bar code symbol. Next, the user manually activates the scanner to initiate reading, and then moves the scanner over other objects bearing bar code symbols to be read. Prior art bar code symbol readers illustrative of this first category are disclosed in U.S. Pat. Nos. 4,387,297 to Swartz; 4,575,625 to Knowles; 4,845,349 to Cherry; 4,825,057 to Swartz, et al.; 4,903,848 to Knowles; 5,107,100 to Shepard, et al.; 5,080,456 to Katz, et al.; and 5,047,617 to Shepard, et al.
The second category of hand-held laser-based bar code symbol readers includes automatically actuated systems having lightweight triggerless hand-held laser scanners which can be supported in the hand of the user. The user positions the hand-held laser scanner at a specified distance from the object bearing the bar code, whereupon the presence of the object is automatically detected. The presence of the bar code symbol on the object is also detected, and thereafter the detected bar code symbol automatically read. Prior art illustrative of this second category of laser-based bar code symbol reading systems are disclosed in U.S. Pat. No. 4,639,606 to Boles, et al., and 4,933,538 to Heiman, et al.
Presently, there are basically two methods of interconnecting a hand-held laser-based bar code scanner to a base station which, depending on the particular application, may be either a controller, a keyboard-scanner interface device, or a central or host computer. The first method of interconnection employs physical wiring between each hand-held bar code scanner and an associated base unit. Typically, the physical wiring is realized as flexible cord having a coiled structure to permit elongation as required during bar code symbol reading operations.
A major drawback with bar code symbol reading systems using the physical-wiring method of interconnection is that the movement of the portable hand-held laser scanning device is restricted by the overall (extended) length of the flexible cord. In many applications, such as product inventory, the use of such bar code symbol reading systems is simply unacceptable. The second method of interconnection employs a xe2x80x9cwirelessxe2x80x9d electromagnetic communication link between each hand-held bar code scanner (or reader) and its associated base unit. Typically, the electromagnetic communication link is established by transmitting and receiving electromagnetic signals over the radio-frequency (RF) or infra-red (IR) region of the electromagnetic spectrum. Examples of such systems are disclosed in U.S. Pat. Nos. 4,418,277 to Tremmel, et al. and 5,157,687 to Tymes, and in the U.S. Patents cited therein.
While prior art bar code symbol reading systems employing the wireless method of interconnection offer a marked degree of flexibility over systems utilizing the physical wiring method, such systems nevertheless suffer from a number of shortcomings and drawbacks. In particular, these systems require two-way packet communications which involves the use of complex data communications protocols and a separate transmitter and a receiver (i.e., transceiver) at each hand-held bar code symbol reader and base unit in the system. Typically, these data communications requirements increase the cost of manufacture of such systems, and substantially increase the electrical power consumed by each hand-held bar code symbol reader.
Thus, there is a great need for a bar code symbol reading system and method which overcomes the above-described shortcomings and drawbacks without compromising system performance and versatility.
Accordingly, it is a primary object of the present invention to provide a bar code symbol reading system having at least one hand-supportable bar code symbol reading device which, after successfully reading a code symbol, automatically constructs and then transmits a data packet to a base unit positioned within the data transmission range of the bar code symbol reading device.
It is another primary object of the invention to provide a bar code symbol reading system which, upon successful receipt of the transmitted data packet and recovery of symbol character data therefrom, employs a base unit that generates an acoustical acknowledgment signal. This acknowledgment signal is perceptible to a user of the bar code symbol reading device who is located within the data transmission range thereof.
A further object of the present invention is to provide such a system with one or more automatic (i.e., triggerless) hand-supportable laser-based bar code symbol reading devices, each of which is capable of automatically transmitting data packets to its base unit after successfully reading a bar code symbol.
A further object of the present invention is to provide such a bar code symbol reading system in which the hand-supportable bar code symbol reading device can be used as a portable hand-supported laser scanner in an automatic hands-on mode of operation, or as a stationary laser projection scanner in an automatic hands-free mode of operation.
A further object of the present invention is to provide such a bar code symbol system, in which the base unit is adapted to mechanically support the hand-supportable bar code symbol reading device in its automatic hands-free mode of operation.
A further object of the present invention is to provide such a bar code symbol system in which the base unit contains a battery recharging device that automatically recharges batteries contained in the hand-supportable device when the hand-supportable device is supported within the base unit.
It is another object of the present invention to provide such an automatic bar code symbol reading system with a mode of operation that permits the user to automatically read one or more bar code symbols on one or more objects in a consecutive manner.
A further object of the present invention is to provide such an automatic bar code symbol reading system, in which a plurality of automatic hand-supportable bar code symbol reading devices are used in conjunction with a plurality of base units, each of which is mated to a particular bar code symbol reading device.
A further object of the present invention is to provide such an automatic bar code symbol reading system, in which radio frequency (RF) carrier signals of the same frequency are used by each hand-supportable bar code symbol reading device to transmit data packets to respective base units.
A further object of the present invention is to provide such an automatic bar code symbol reading system, in which a novel data packet transmission and reception scheme is used to minimize the occurrence of data packet interference at each base unit during data packet reception.
A further object of the present invention is to provide such an automatic bar code symbol reading system, in which the novel data packet transmission and reception scheme enables each base unit to distinguish data packets associated with consecutively different bar code symbols read by a particular bar code symbol reading device, without the transmission of electromagnetically-based data packet acknowledgment signals after receiving each data packet at the base unit.
A further object is to provide such an automatic bar code symbol reading device, in which the automatic hand-supportable bar code (symbol) reading device has an infrared (IR) based object detection field which spatially encompasses at least a portion of its visible laser light scan field along the operative scanning range of the device, thereby improving the laser beam pointing efficiency of the device during the automatic bar code reading process of the present invention.
Another object of the present invention is to provide such an automatic bar code symbol reading system, in which the base unit has a support frame that supports the hand-supportable housing of the device in a selected mounting position, and permits complete gripping of the handle portion of the hand-supportable housing prior to removing it from the support frame.
A further object of the present invention is to provide such an automatic bar code symbol reading system, in which the hand-supportable bar code reading device has long and short-range modes of object detection, bar code symbol detection and/or bar code symbol reading. The long and short range modes of object detection may be manually selected by the user by way of manual activation of a switch on the hand-supportable housing of the device. In one illustrative embodiment, the long-range modes of object detection may be automatically selected when the hand-supportable bar code reading device is placed within the support stand during the hands-free mode of operation. In this embodiment, the short-range mode of object detection is automatically selected whenever the hand-supportable bar code reading device is removed from the support stand and used in its hands-on mode of operation.
In another embodiment, the short range mode of bar code presence detection may be automatically selected upon decoding a predesignated bar code symbol preprogrammed to induce the short-range mode of bar code presence detection. In the short-range mode of bar code presence detection, the automatic bar code reading device not only detects the presence of a bar code within the scan field by analysis of collected scan data, but it further processes the collected scan data to produce digital count data representative of the measured time interval between bar and/or space transitions. Bar code symbols that are present within the short range of the scan field will produce scan data having time interval characteristics falling within a prespecified timing data range. Using the results of this analysis, only bar code symbols scanned within the short-range field are deemed xe2x80x9cdetected,xe2x80x9d and only bar code symbols detected within the short-range of the scan field activate the decoding module of the device and thus enable bar code symbol reading.
A further object of the present invention is to provide such an automatic bar code symbol reading system, in which the hand-supportable bar code reading device has long and short range modes of bar code symbol reading within its scan field. In the short-range mode of bar code symbol reading, the only decoded bar code symbols residing within the short-range portion of the scan field, are deemed xe2x80x9creadxe2x80x9d.
Another object of the present invention is to provide an automatic hand-supportable bar code reading device which has both long and short-range modes of object detection and bar code symbol reading that are automatically selectable by placing the hand-supportable device within its support stand and removing it therefrom. Pursuant to this particular embodiment of the present invention, the automatic bar code symbol reading system can be used in various bar code symbol reading applications, such as, for example, charge coupled device (CCD) scanner emulation and bar code xe2x80x9cmenuxe2x80x9d reading in the hands-on short-range mode of operation, and counter-top projection scanning in the hands-free long-range mode of operation.
An even further object of the present invention is to provide an automatic hand-supportable bar code reading device which prevents multiple reading of the same bar code symbol due to dwelling of the laser scanning beam upon a bar code symbol for an extended period of time.
A further object of the present invention is to provide a point-of-sale station incorporating the automatic bar code symbol reading system of the present invention.
It is a further object of the present invention to provide an automatic hand-supportable bar code reading device having a control system which has a finite number of states through which the device may pass during its automatic operation, in response to diverse conditions automatically detected within the object detection and scan fields of the device.
It is yet a further object of the present invention to provide a portable, fully automatic bar code symbol reading system which is compact, simple to use and versatile.
Yet a further object of the present invention is to provide a novel method of reading bar code symbols using an automatic hand-supportable laser scanning device.
A further object of the present invention is to provide a wireless automatic bar code symbol reading device having a housing that can be comfortably mounted to the wrist of its user, similar to a wrist bracelet or a watch, and which can be reconfigured when not in use to provide its user greater hand mobility.
A further object of the present invention is to provide such a bar code symbol reading, in which the laser scanning plane thereof extends upwardly, downwardly, or laterally transverse to the pointing direction of the wearer""s hand on which the device is mounted.
A further object of the present invention is to provide such a bar code symbol reading system, in which the base unit functions as a xe2x80x9cdesktop wedgexe2x80x9d (i.e., keyboard interface device) for interfacing a keyboard and the bar code symbol reading device with a computer, so that xe2x80x9ckeyboard-scan formattedxe2x80x9d data produced from the keyboard and the bar code reading device is identically formatted for entry into the computer through a single data input port, and subsequent processing therein.
A further object of the present invention is to provide a desk-top bar code symbol reading having a base unit with a small bar code symbol printing engine.
An even further object of the invention is to provide such a bar code reading system, in which the base unit is realized as a PCMCIA card installable in the PCMCIA port of personal computer system, including notebook computers, palm top computers, personal digital assistant devices, desk-top computers and the like.
A further object of the present invention is to provide a point-of-sale station incorporating the automatic bar code symbol reading system of the present invention.
These and further objects of the present invention will become apparent hereinafter and in the claims.